Tweaks

Signed-off-by: Carlos Agüero <[email protected]>

ros_gz_sim_demos/README.md

@@ -58,10 +58,20 @@ Send commands to a differential drive vehicle and listen to its odometry.
 
     ros2 launch ros_gz_sim_demos diff_drive.launch.xml
 
-Then send a command.
+Then send a command
 
     ros2 topic pub /model/vehicle_blue/cmd_vel geometry_msgs/msg/Twist "{linear: {x: 5.0}, angular: {z: 0.5}}"
 
+This demo also shows the use of custom QoS parameters. The commands are
+subscribed to as "reliable", so trying to publish "best-effort" commands
+won't work. See the difference between:
+
+    ros2 topic pub /model/vehicle_blue/cmd_vel geometry_msgs/msg/Twist "{linear: {x: 5.0}, angular: {z: 0.0}}" --qos-reliability reliable
+
+And
+
+    ros2 topic pub /model/vehicle_blue/cmd_vel geometry_msgs/msg/Twist "{linear: {x: 5.0}, angular: {z: 0.0}}" --qos-reliability best_effort
+
 ![](images/diff_drive_demo.png)
 
 ## Depth camera

ros_gz_sim_demos/config/diff_drive.yaml

@@ -1,36 +1,24 @@
 # Diff drive configuration.
-- ros_topic_name: "/model/vehicle_blue/cmd_vel"
-  gz_topic_name: "/model/vehicle_blue/cmd_vel"
+- topic_name: "/model/vehicle_blue/cmd_vel"
   ros_type_name: "geometry_msgs/msg/Twist"
   gz_type_name: "gz.msgs.Twist"
-  subscriber_queue: 5
-  publisher_queue: 6
-  lazy: false
+  lazy: true
   direction: ROS_TO_GZ
 
-- ros_topic_name: "/model/vehicle_blue/odometry"
-  gz_topic_name: "/model/vehicle_blue/odometry"
+- topic_name: "/model/vehicle_blue/odometry"
   ros_type_name: "nav_msgs/msg/Odometry"
   gz_type_name: "gz.msgs.Odometry"
-  subscriber_queue: 5
-  publisher_queue: 6
-  lazy: false
+  lazy: true
   direction: GZ_TO_ROS
 
-- ros_topic_name: "/model/vehicle_green/cmd_vel"
-  gz_topic_name: "/model/vehicle_green/cmd_vel"
+- topic_name: "/model/vehicle_green/cmd_vel"
   ros_type_name: "geometry_msgs/msg/Twist"
   gz_type_name: "gz.msgs.Twist"
-  subscriber_queue: 5
-  publisher_queue: 6
-  lazy: false
+  lazy: true
   direction: ROS_TO_GZ
 
-- ros_topic_name: "/model/vehicle_green/odometry"
-  gz_topic_name: "/model/vehicle_green/odometry"
+- topic_name: "/model/vehicle_green/odometry"
   ros_type_name: "nav_msgs/msg/Odometry"
   gz_type_name: "gz.msgs.Odometry"
-  subscriber_queue: 5
-  publisher_queue: 6
-  lazy: false
+  lazy: true
   direction: GZ_TO_ROS

ros_gz_sim_demos/launch/diff_drive.launch.xml

@@ -1,6 +1,14 @@
 <launch>
-  <gz_server world_sdf_file="diff_drive.sdf" use_composition="True" create_own_container="True" />
-  <ros_gz_bridge bridge_name="ros_gz_bridge" config_file="$(find-pkg-share ros_gz_sim_demos)/config/diff_drive.yaml" use_composition="True" />
+  <gz_server
+    world_sdf_file="diff_drive.sdf"
+    use_composition="True"
+    create_own_container="True" />
+  <ros_gz_bridge
+    bridge_name="ros_gz_bridge"
+    config_file="$(find-pkg-share ros_gz_sim_demos)/config/diff_drive.yaml"
+    use_composition="True"
+    bridge_params="'qos_overrides./model/vehicle_blue.subscriber.reliability': 'reliable',
+                   'qos_overrides./model/vehicle_green.subscriber.reliability': 'reliable'" />
   <node pkg="rviz2" exec="rviz2" args="-d $(find-pkg-share ros_gz_sim_demos)/rviz/diff_drive.rviz" />
   <executable cmd="gz sim -g" />
 </launch>